Process for producing dies

ABSTRACT

In a method for producing embossing plates, in particular steel intaglio printing plates, a plane element is determined from a line drawing, the edge of the plane element defining a desired contour. A tool track is then calculated from the desired contour and a desired depth associated with the plane element, to be used for guiding an engraving tool such that the partial area is removed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for producing embossing plates, inparticular steel intaglio printing plates.

2. Description of Related Art

For producing embossing plates, in particular steel intaglio printingplates, as are usually employed for printing high-quality printedproducts such as papers of value, bank notes or the like one hashitherto resorted to having the embossing plates produced in anelaborate method by an artist. A picture motif made available to theartist is converted into a line pattern whereby lines of differentwidth, depth and a different number per unit area represent the graylevels of the original. Using a chisel, the artist brings this motif intime-consuming hand labor into the metal plate, for example steel orcopper. The thus produced plates are characterized by their high qualitywith respect to use in steel intaglio printing. However thepossibilities of correction are extremely low for the artist duringproduction of the plate. If this original plate is damaged or lost, noidentical plate can be produced since each plate is an individualproduction.

It is also known to perform the engraving of a printing cylinder bymachine. As described in EP 0 076 868 B1 for example, cups are broughtinto the printing form which represent the gray level value of a masterdepending on their screen width and engraving depth. Light tones andtone-dependent changes in the master are produced by varying the focalvalue of the electron beam in the printing form, whereby cups ofdifferent volume can arise.

From DE 30 08 176 C2 it is also known to use a laser for engraving aprinting cylinder. An original is scanned and the resulting signal usedvia an analog-to-digital converter for controlling the laser with whichengraved cups of defined depth and extension are brought into theprinting cylinder.

When the original is broken down into gray-level values represented onthe printing plate by cups, the essential components necessary for steelintaglio printing are lost, since this technique is only able totransfer ink to the print carrier point by point. Steel intaglioprinting, however, is characterized by the fact that a continuous linearprinting pattern tangible with the inking is transferred to the printcarrier, characterized in particular by its filigreed design.

SUMMARY OF THE INVENTION

The objective of the invention is accordingly to propose a methodpermitting simple and automated production of embossing plates, inparticular steel intaglio printing plates.

The invention is based on the finding that it is possible to treat atwo-dimensional line original graphically such that the existing linesare interpreted as areas. These areas are limited by edges, these edgesdefining a desired contour of the area. Starting out from this desiredcontour one determines a tool track along which an engraving tool can beguided such that material is removed within the area limited by thedesired contour. The engraving tool is controlled such that the materialwithin the desired contour is removed in the form of continuous orinterrupted lines or grooves in a certain depth profile. This depthprofile can be determined by a depth value that is constant or varieswithin the desired contour.

The inventive method preferably makes use of a data processing systemwhich makes it possible to acquire, store and process two-dimensionalline originals. The two-dimensional line original, which is for exampleproduced in a computer or read in via input devices, can be processedwith the ad of a suitable computer program so as to yield track data forcontrolling an engraving tool along a tool track. For this purpose onedefines in a first working step from the two-dimensional line original aplane element which consists for example of a single line of the lineoriginal. The edge enclosing the line then defines a desired contourwith is intersection-free. To produce the engraving one associates adepth profile with the interior of the plate element as the desireddepth for the engraving, and then calculates from the desired contourdata and the associated desired depth a tool track along which theengraving tool is guided and removes material within the plane elementin a predetermined, non-random manner.

This procedure is then repeated for each individual plane element to beengraved so that an engraving tool track can be determined for theentire area to be engraved, composed of the sum of the individual planeelements to be engraved.

Using this method one can considerably increase the speed for producingthe embossing plate. Furthermore, errors during engraving are excludedby the exact guidance of the engraving tool so that a multiplicity ofembossing plates can be produced with the same exactness. In additionthe method offers simple possibilities of correction by changing thedata of the line drawing. The exact reproducibility of the engraving tobe brought in furthermore permits printing plates to be produceddirectly without any need for a galvanic shaping process. Severalengraving tools can thereby also engrave several plates simultaneously.Furthermore several, possibly different, engraving tools can also becontrolled such that they process a plate simultaneously, therebyoptimizing the processing time.

Further advantages and advantageous embodiments will be explained withreference to the following figures, in which a true-to-scalerepresentation was dispensed with for the sake of clearness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematized overall view of the inventive method,

FIG. 2 shows a schematic example of the inventive method,

FIG. 3 shows a schematic example of the inventive method,

FIG. 4 shows a schematic example of the inventive method,

FIG. 5 shows a schematic example of the inventive method,

FIG. 6 shows a schematic cross section through an embossing plate,

FIG. 7 shows a schematic example of the inventive method,

FIG. 8 shows a schematic example of a tool track,

FIG. 9 schematically shows two tool point forms,

FIG. 10 shows a schematic cross section through an embossing plate,

FIG. 11 shows a schematic cross section through an embossing plate.

FIG. 12 shows a schematic example of the inventive method with therotating chisel of FIG. 4 replaced by a laser beam.

FIG. 13 shows another schematic example of the inventive method, withtwo rather than one rotating chisels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, the inventive method starts out from two-dimensionalline original 1, consisting of simple black line 2 on light background 3to illustrate the inventive principle. The original, which is present onpaper for example, can be digitally acquired in a computer with the aidof a scanner or another suitable data input means. Alternatively it isalso possible to produce the line original directly on the computerinteractively, using for example a plotting or graphics program, or tohave the computer produce certain graphic data by mathematicalalgorithms. If the original is designed in the latter way, guillochelines or other graphic elements could be produced for example with theaid of implemented programs which permit interactive input or presettingof data or calculation of the structures with the aid of randomalgorithms. From line original 1 one defines in a second method step anarea, e.g. area 4, which represents a partial area of the plate. Theedge of this area defines desired contour 5 which serves as the first oftwo elements as the starting point for subsequent calculation of a tooltrack along which the embossing plate is to be engraved. As the secondelement for calculating the tool track it is necessary to associate adepth profile within the desired contour, which is termed the so-calleddesired depth. This can be preset constantly for the entire engravingfor example. It can also depend on the form of the engraving tool used.From desired depth 6 and desired contour 5 one then calculates tooltrack 10 located within area 4 along which the engraving tool must bemoved so that the engraving corresponding to the line drawing can bebrought into the embossing plate.

Since different engraving tools can be used for engraving the plate, itis clear that data of the particular engraving tool also enter into thecalculation of the tool track. If a laser beam is used, the width of thebeam acting on the embossing plate can be included in the calculationfor example. If a mechanical chisel is used, the chisel form, inparticular the form of the point or its radius of curvature, is ofessential importance for calculating the tool track.

The engraving tool is controlled subsequent to the determination of thetool track such that it moves within area 4, does not hurt desiredcontour 5 during engraving and removes area 4 at predetermined desireddepth 6.

In a specific embodiment, shown in FIG. 2, the number “7” is produced asa line original on a sheet of paper and read into a computer with theaid of a scanner. The number “7” consists of lines 7, as shown in FIG.2(a). Using the above-described procedure one defines from existinglines 7 areas 8 whose edges form desired contours 9, as shown in FIG.2(b). These serve as a starting point for calculating a tool track.Through the association of a desired depth, which is constant in thiscase, one can determine with consideration of the particular tool datatool tracks 10, 11 and 12 along which the engraving tool is controlledover the embossing plate so that the line drawing can be transferred tothe embossing plate. These tool tracks are shown by way of example inFIG. 2(c). Tool tracks 10, 11 and 12 are preferably determined such thatthe tool is guided along desired contours 9 within areas 8 withouthurting the desired contours.

Since the width of the material removed with the engraving tool islimited, one can define via the line drawings plane elements with a sizewhich cannot be removed completely if the engraving tool is guided onlyalong the desired contour lines. A very simple form of line drawing isshown by way of example in FIG. 3. Via the line drawing of FIG. 3(a) onedefines plane element 8 having contour line 9. When tool track 13 is nowcalculated on the basis of these given data, as shown in FIG. 3(b), theengraving tool cannot in one cycle completely remove the area to beremoved, depending on the dimensioning of area 8 and the form of theengraving tool.

For rotating 14 chisel these relations are shown in perspective in FIG.4. Corresponding relations for a laser beam 35 generated by a laser beamsource 34 are shown in FIG. 12, with element common to FIGS. 4 and 12being numbered identically. For convenience, the following discussionwill refer only to chisel 14, but it will be understood that theautomation principles described below apply to the laser engraverillustrated in FIG. 12 as well as to the mechanical chisel illustratedin FIG. 4. In addition, it will be understood that the principlesdescribed below are applicable the simultaneous use of multipleengraving tools 36 and 37 on a single embossing plate 38, as illustratedin FIG. 13. Chisel 14 rotates about its own axis z and, afterpenetrating into embossing plate 15, removes material from the embossingplate along tool track 13 at a predetermined depth. Due to the guidanceof rotating chisel 14 along tool track 13, desired contour line 9remains intact. Because of the limited width of the chisel, however,residual area 16 of area 8 to be removed cannot be removed in one cycleof the engraving tool. Only in a further operation can residual area 16be removed using a second predetermined tool track, which can differ inform from first tool track 13.

As to be seen in FIG. 5(a), it is necessary in this case also toconsider residual area 16 not removable in the first step whencalculating the tool track for removing area 8. For removing residualarea 16 one can determine different tool tracks depending on the desiredengraving results. Thus the tool track can, as shown in FIG. 5(b), firstextend along the desired contour and residual area 16 then be removed ina meander shape, the engraving tool removing the residual areacontinuously in meander-shaped track 17 within area 16. FIG. 5(c) showsa further possibility whereby residual area 16 is removed by guidance ofthe engraving tool along tool tracks which are similar in themathematical sense to tool track 12 first calculated, i.e. tool tracks18, 19 and 20 correspond to tool track 12 in form but have a differentdimension from tool track 12. Particularly in the case of curved contourlines, residual area 16 can accordingly be removed using tool trackswhich extend contour-parallel, i.e. are equidistant from the contourline at each point.

As to be seen in FIG. 6(a) in a cross section through embossing plate15, one calculated from contour line 9 a tool track along which theengraving tool was guided, thereby producing engraved line 28 enclosingresidual area 16 yet to be engraved. To remove residual area 16 one canuse any method but preferably one of the above-described. Regardless ofthe particular method one produces at the base of the residual areaengraving a defined roughness structure determined by the offset andform of the engraving tool. FIG. 6(b) shows such a roughness structure,whereby a tapered, rotating graver was used for engraving, removing theembossing plate at defined depth T. The chisel used had diameter D onthe surface emerging from the embossing plate and was offset inward bythe amount d/2 during removal of the residual area, while the offset is¾ d in the example shown in FIG. 6(c). The engraving tool was moved inaccordance with the tool tracks shown in FIG. 5(c) in both examples.

The described surface structuring at the base of the engraved area hasseveral advantages for producing steel intaglio printing plates. Usingsteel intaglio printing plates one could hitherto print only limitedline widths, due to the fact that the steel intaglio printing ink canonly be brought into engravings of the plate which have a certainmaximum width. This obstacle is eliminated by the newly proposedengraving since one can now adjust the roughness as a base pattern atthe base of the engraving to serve as an ink trap for a steel intaglioprinting ink brought in. This ink can thus be held even in very wideengraved lines so that it is now possible for the first time to printwide lines by steel intaglio printing. As shown in FIGS. 6(b) and 6(c),the roughness of the base can be controlled via the size of theengraving tool offset. Since different offset widths of the chisel canalso be considered in the calculation of the tool track, the roughnesscan be different at the base in different areas of the residual area andthus the engraved line or area be superimposed with an additionalmodulation of the roughness of the base pattern. It is thus alsopossible to bring further information into an engraved line solely byselectively producing the roughness of the base pattern.

Since transparent inks are usually employed in steel engraving, adifferent color effect within a line can be produced on the document tobe printed with the aid of the different engravings within a line. Thiscolor effect can be improved further in particular if the engravingalready produced is provided in a further method step with a secondengraving whose desired depth has a different definition from that ofthe first engraving. FIG. 7 shows an example of this in which linedrawing 18 with lines 19 is present. Lines 19 are limited by desiredcontour lines 20. Within lines 19 there are areas 21 limited in turn bysecond desired contour lines 22. This line original is brought into acomputer as a digital data image or produced directly therein. As shownin a detail in FIG. 8, one calculates from contour lines 20, togetherwith a desired depth firmly preset in this case, tool track 23 alongwhich a first engraving takes place. Any remaining residual area isremoved at a given desired depth, as described above. Area 21 locatedwithin line drawing 19 is converted into tool track 24 in the same way,the contour of area 21 and a second desired depth different from thefirst being included in the determination of the tool track as a basisfor conversion. One can thus produce engravings containing additionalinformation even over a large surface area, which can be transferred tothe document at the same time by the steel intaglio printing process.

The tapered edges of line drawing 19 can be rendered exactly by asuitable choice of chisel form. It is possible to use a single finechisel for the engraving, or rework the tapered edges with a fine chiselafter engraving the area with a coarse chisel. As an alternative to thispossibility one can also adapt the depth profile to the requirements ofarea 19 to be engraved. In this case the depth profile is preset suchthat the engraving tool removes less material at the tapered edges sothat, in particular if a rotating mechanical chisel is used, the chiselemerges ever further out of the material to be processed and due to theconic form therefore the removed line becomes narrower. These twotechniques can also be used for exact engraving of corners or edges.

For determining the tool track one generally combines a determineddesired contour with an engraving depth profile according to theinventive method, thus determining from these two data a tool trackalong which the engraving tool is guided, so that the material can beremoved in accordance with the line drawing at the depth correspondingto the depth profile. The depth profile, i.e. the desired depth, can bepreset for each individual engraved line or for the engraving altogetheras a constant. Desired depths can also be different for individualengraved lines or parts of engraved lines, so that the particular tooltrack is accordingly modulated. In addition it is possible to usedifferent engraving tools of like or different kinds in successivemethod steps in order to produce the desired engraving result. Ifrotating mechanical chisels are used it is especially advantageous touse different chisel points, forms and sizes, so that optimal embossingplates can be produced in this way.

By producing and using different chisel forms and sizes one caninfluence the embossing result in a variety of ways. Precisely the formand size of the embossing tool determine the form of the thus producedengraving cross-sectional area, depending on the penetration depth ofthe engraving tool into the plate. FIG. 9 shows two examples of possiblecross-sectional areas of chisel points. In FIG. 9(a) the chisel point isformed so that intersecting line 28 of the envelope of the cone forms a45° angle with axis of rotational symmetry S of the engraving tool.Engraving the plate with this tool thus results in an engraving trackwhose side walls likewise run to the base of the engraving at a 45°angle. This example shows that different wall inclinations can beproduced in the engraving plate by producing gravers with differentangles. Along with the wall gradient one can also influence the wallform via the forming of the engraving tool. FIG. 9(b) shows in thisconnection cross-sectional line 29 of a rotationally symmetric engravingpoint with which different angular degrees of the engraving walls can beproduced at different engraving depths. These two examples indicate thatthe use of different engraving tools considerably influences the desiredengraving result, and optimal results can be achieved for a certain lineoriginal with the aid of specially produced engraving tools or engravingtool points. In particular it is possible to produce the engraving toolsin their angle and form so that they can remove even very fine areas tobe engraved, whereby in the case of fine lines the tool track alongwhich the engraving tool is guided leads along the predetermined lineonly once within the area to be removed. Due to the special form of theengraving tool, the material within the desired contour is thus removedby a single working traverse of the graver. In these cases, the tooltrack can also lead along a center line located between two desiredcontour lines and equidistant from the two. A suitable chisel form mustthen be selected at a given depth profile.

The inventive method offers the crucial advantage that engraving can beperformed with exact line control even with extremely small engravingareas or lines. The desired depths which can be reached with theinventive method are preferably between 10 and 150 microns, whereby thedesired depths can also be preset by different gray-level values of theline original.

If the original is formed for example by a uniform line pattern, e.g. aguilloche, one can bring in visible information, for example a portrait,by varying the line depth, line width, line density or contour by themethod described above. Instead of visually recognizable information,however, one can also bring in different, for example machine-readable,information in this way.

Although the use of different engraving tools already provides a wealthof possibilities for bringing into the embossing plate substructures inthe form of defined roughness structures at the base of the engraving,as shown in FIGS. 6 b and 6 c, or additional information resulting fromthe second engraving described above and illustrated in FIGS. 7 and 8,which can be called micro-engraving in the present case, the inventivemethod can of course also be used to modify the flanks of the engravingalong the desired contours. FIG. 10 shows an example of bringingmicro-engraving into the flanks of the depression shown, for example, inFIGS. 6 b and 6 c, whereby an engraving consisting in the present caseof flank 28 and engraving 29 located on the bottom of the depression isbrought into embossing plate 15 and, in an additional operation,additional information in the form of so-called micro-engraving ormicrostructure lines 30 was brought into flank 28. The flank of theengraved line, like the bottom of the engraved lines as described abovein connection with FIGS. 7 and 8, can thus be provided with anadditional information content which can consist for example of simplelines, a step function, characters, patterns, pictures or the like. Inparticulars in the case of gently sloping flanks 28 it is therefore alsopossible to bring additional information into the flank of an engravedline which extends downward from desired contour line 26.

The inventive method can of course also be employed if a negative imageof the line original is to be produced. As shown in FIG. 11, theabove-described calculation of the tool track can also be performed iffurther surface area 25 to be excluded from removal is located withinthe area to be removed. The tool track is preferably calculated so thatthe engraving tool runs down the workpiece, i.e. the embossing plate, ina first step such that the embossing plate is removed along desiredcontour line 26. In a further step, the engraving tool is guided alongsecond desired contour 27 while a residual area possibly remainingbetween desired contours 26 and 27 is cleared out, as described above.

1. A method for producing an intaglio printing plate having a flat topsurface with at least one depression in the form of a line brought intothe surface of the intaglio printing plate and arranged to be filledwith printing ink during intaglio printing, comprising the steps of:providing a two-dimensional line original; defining from thetwo-dimensional line original a line to be brought into the surface ofthe intaglio printing plate, said line defining a limited partial area,an edge of the limited partial area defining a desired contour;associating a depth profile, selected based on the amount of printingink to be used in printing, within the desired contour; calculatingtrack data with aid of a computer program for controlling movement of anengraving tool along a tool track to be followed by the engraving toolwithin the desired contour based on the desired contour and thepredetermined desired depth profile; and controlling the movement of theengraving tool along said tool track according to said track data suchthat a material of the surface of the intaglio printing plate is removedwithin the desired contour along the predetermined desired depth profileto form said at least one depression, said tool track being continuous.2. The method of claim 1, characterized in that at least part of thetool track extends contour-parallel to the desired contour.
 3. Themethod of claim 1, characterized in that the desired depth is variablewith the tool track.
 4. The method of claim 1, characterized in that thedesired depth is constant within the tool track.
 5. The method of claim1, characterized in that the material is removed along the tool trackwithin the desired contour by a single working traverse of the engravingtool.
 6. The method of claim 1, characterized in that an unengravedresidual area located within the partial area is removed along a secondtool track.
 7. The method of claim 6, characterized in that the residualarea is removed by controlling the engraving tool such that said toolremoves a surface of the residual area in tracks which are similar orcontour-parallel to the desired contour.
 8. The method of claim 6,characterized in that the residual area is removed by controlling theengraving tool such that a surface of the residual area is removed in ameander shape.
 9. The method of claim 6, characterized in that theunengraved residual area is removed such that a new surface of definedroughness arises at a base of an engraving resulting from removal of theunengraved residual area.
 10. The method of claim 9, characterized inthat the engraving tool is controlled such that the roughness isexecuted in the form of grooves.
 11. The method of claim 1,characterized in that at least part of the partial area from whichmaterial is removed at a predetermined depth is deepened further in atleast one further engraving step.
 12. The method of claim 11,characterized in that the at least one further engraving step produceshumanly recognizable or machine-readable information.
 13. The method ofclaim 11, characterized in that the at least one further engraving stepis executed with a finer engraving tool than the engraving tool used toremove said partial area within the desired contour.
 14. The method ofclaim 13, characterized in that the at least one further engraving stepis performed in a flank sloping from the desired contour.
 15. The methodof claim 1, characterized in that the desired contour is defined withthe aid of a data processing system.
 16. The method of claim 1,characterized in that the engraving tool is a laser beam.
 17. The methodof claim 1, characterized in that the engraving tool is a mechanicalchisel.
 18. The method of claim 17, characterized in that the mechanicalchisel rotates during engraving.
 19. The method of claim 1,characterized in that characterized in that engraving tools of differentkinds or dimensions are used for producing the intaglio printing plate.20. The method of claim 1, characterized in that said plate is engravedwith multiple engraving tools simultaneously.
 21. The method of claim 1,characterized in that the intaglio printing plate is a steel intaglioprinting plate.
 22. The method of claim 1, further comprising takinginto account the width of said tool before forming said desired contour.23. The method of claim 1, further comprising forming a seconddepression to define a second desired contour and a second limitedpartial area in said limited partial area; moving the engraving toolalong a second tool track in said second limited partial area at asecond penetration depth; and taking into account the width of said toolbefore forming said desired contour and said second desired contour. 24.The method of claim 1, further comprising the forming of a seconddepression to define a second desired contour and a second limitedpartial area in said limited partial area, said tool track in saidsecond limited partial area being a second penetration depth.
 25. Anintaglio printing plate having a surface with at least one engraveddepression in the form of a line, said at least one depression beingarranged to be filled with printing ink during intaglio printing, saidat least one depression having flanks, a bottom, and an engraved definedroughness structure at a bottom of the at least one depression, whereinsaid defined roughness structure has a predetermined meander-shape orextends at least in partial areas in a predetermined direction parallelto a direction of said at least one line.
 26. The embossing or intaglioprinting plate of claim 25, characterized in that the at least onedepression further comprises micro-engraving that representsinformation.
 27. The embossing or printing plate of claim 26,characterized in that the micro-engraving is incorporated in the form ofcharacters, pictures, or patterns.
 28. The embossing or intaglioprinting plate of claim 26, characterized in that said informationextends over multiple depressions.
 29. The embossing or intaglioprinting plate of claim 25, characterized in that the defined roughnessstructure represents machine readable information.
 30. The embossing orintaglio printing plate of claim 25, characterized in that the definedroughness structure is executed in the form of grooves.
 31. Theembossing or intaglio printing plate of claim 25, characterized in thatthe defined roughness structure is brought in with the aid of a laserbeam.
 32. The embossing or intaglio printing plate of claim 25,characterized in that the defined roughness structure is brought in witha mechanical chisel.
 33. A method for producing an intaglio printingplate having a flat top surface with at least one depression in the formof a line brought into the surface of the intaglio printing plate andarranged to be filled with printing ink during intaglio printing,comprising the steps of: providing a two-dimensional line original;defining from the two-dimensional line original a line to be broughtinto the surface of the intaglio printing plate, said line defining alimited partial area, an edge of the limited partial area defining adesired contour; associating a depth profile, selected based on theamount of printing ink to be used in printing, within the desiredcontour; calculating track data with aid of a computer program forcontrolling movement of an engraving tool along a tool track to befollowed by the engraving tool within the desired contour based on thedesired contour and the predetermined desired depth profile; andcontrolling the movement of the engraving tool along said tool trackaccording to said track data such that a material of the surface of theintaglio printing plate is removed within the desired contour along thepredetermined desired depth profile to form said at least onedepression, said tool track being continuous and extending along thedesired contour; and removing an unengraved residual area located withinthe partial area long said tool track.